1. Field of the Invention
The present invention relates generally to medical devices, and more particularly to an improved tip design for a multi-lumen catheter.
2. Description of Related Art
Multi-lumen catheters are used for a variety of applications when it is necessary to have two separate fluid pathways. One such application for a multi-lumen catheter is for use in a hemodialysis process. During hemodialysis, a dual-lumen catheter can be employed to simultaneously accommodate opposing blood flow. More specifically, one lumen carries blood from a patient to a dialysis machine where it is processed for the removal of toxins, while the opposing lumen returns the purified blood to the patient.
Multi-lumen catheters are well known in the art. An example of such a catheter which is used for hemodialysis is shown in U.S. Pat. No. 4,808,155 to Mahurkar, which discloses a double lumen catheter including a return lumen and an inlet lumen. The return lumen extends along the entire length of the catheter to an opening at the distal end of the catheter. The inlet lumen is shorter than the return lumen and terminates at an opening substantially displaced from the return opening. The separation of the two openings is designed to prevent the mixing of treated blood with non-treated blood. Problems may result from this design, however. First, the openings may become partially or totally occluded by the vessel wall or by a build up of blood components. Second, due to the pressure of fluid exiting the return lumen, a whipping action can occur, wherein the sharp edges of the tip of the catheter lashes back and forth within the vein of a patient, causing trauma to the inside wall of the vein. This whipping action can also cause clots to form around the outside surface of the catheter, obstructing blood flow to and from the openings.
To overcome the problems of the Mahurkar device, Cruz et al. (U.S. Pat. No. 5,571,093) proposed a multi-lumen catheter with a bolus tip, containing a radial passage that forms a port through the side of the bolus. In one embodiment, a first and second lumen are in fluid communication with the port. In another embodiment, the bolus tip contains two ports in the same side, one port providing an opening for the first lumen while the other port provides an opening for the second lumen. In both embodiments, the port nearest to the distal end of the bolus tip is created by removing a piece of the body around greater than 180xc2x0 of the circumference of the body. According to Cruz et al., this configuration causes the velocity of the fluid passing over the bolus to decrease, thereby limiting the whipping action. However, because the outlets of the first and second lumen are located on the same side of the bolus, the problem of mixing treated and non-treated blood exists. Accordingly, there is a need for a catheter tip configuration that maintains adequate separation of treated and non-treated blood and that reduces the traumatic effects associated with whipping. In addition, there is a need for a catheter tip that will not easily become occluded.
It is therefore an object of this invention to provide an improved bolus tip design for a multi-lumen catheter that provides an optimum separation of fluids to be simultaneously injected into and aspirated from a patient""s body.
It is a further object of this invention to provide an improved bolus tip design for a multi-lumen catheter that reduces the trauma to the vein of a patient associated with insertion of the catheter and whipping.
It is still a further object of this invention to provide an improved bolus tip design for a multi-lumen catheter that will allow the continuous transfer of fluid to a patient despite the presence of obstructions.
The present invention provides an improved bolus tip design for use in a multi-lumen catheter for the simultaneous injection and withdrawal of fluids to and from a patient. The bolus tip includes an elongate body preferably made of either silicone or polyurethane, having two channels for fluid flow. The edges of the bolus tip are rounded to prevent unnecessary trauma to the patient""s vein which can occur when the device is initially inserted into the patient, as well as when whipping occurs, which results when fluid being released to the body under pressure causes the device to sway violently back and forth within the vein. An interfacing section at a proximal end of the bolus tip is integrated into the multi-lumen catheter so that the lumens of the catheter match the channels of the bolus tip for uninterrupted flow of fluids therethrough. The integrating of the bolus tip and multi-lumen catheter can be accomplished by one of two procedures. In a first integrating procedure, the bolus tip and catheter are glued together. The outer diameter of the bolus tip at the interfacing point is made slightly greater than that of the multi-lumen catheter so that the catheter can slideably be received by the bolus tip. The bolus tip has a restraining ledge near the bottom of the interfacing section for preventing the further advancement of the catheter during integration. In a second integrating procedure, the bolus tip and catheter are joined through an injection molding process, in which the distal end of a formed catheter is inserted into the bolus tip mold and polyurethane is injected to form the bolus tip with the catheter, resulting in common outer diameters and fluid flow channels.
The two channels, a first channel and a second channel, of the bolus tip run parallel to each other from the catheter to respective outlets, separated by a dividing section. The two channels are generally used for fluid flow, but in certain embodiments, the second channel can be used to house a guide wire for introduction of the catheter into the patient. This is a preferred method of introduction of the catheter over the use of a sheath because of ease, efficiency, and reduced trauma to the patient. The dividing section, in addition to separating the channels, acts as a stabilizing force for the bolus tip by connecting the interfacing section to the nose section. Moreover, in a preferred embodiment, the dividing section also provides a central channel to house the guide wire.
The first channel terminates in a first bolus cavity, which is formed into one side of the bolus tip at a point between the interfacing section and the nose section of the bolus tip. The first bolus cavity extends down to the dividing section in a U-shaped notch, allowing the first channel to be in fluid communication with the surrounding area. The configuration of the first bolus cavity promotes ease of fluid transfer between the bolus tip and the patient, thereby reducing problems associated with the fluid exchange, including whipping and occlusion. Whipping tendency is decreased because the U-shaped configuration effectively slows down the fluid flow. Total occlusion is avoided because even if the surface area of the cavity along the outer diameter of the bolus tip is covered, fluids are still able to enter or exit through the sides of the cavity.
The second channel extends beyond the first channel in the direction of the distal end of the bolus tip. The ending point for the second channel can be configured in one of two ways. In one configuration, the second channel stretches from the interfacing section to the nose section of the catheter. An opening is formed in the end of the catheter which is slightly wider than the second channel itself, facilitating the inlet and outlet of fluids. In another configuration, a second bolus cavity is formed in the side directly opposite the first bolus cavity, located longitudinally between the first bolus cavity and the tip of the nose section. This second bolus cavity also extends to the dividing section in a U-shaped notch, allowing the second channel to be in fluid communication with the surrounding area.
These and other features and advantages of the present invention will become more apparent to those skilled in the art when taken with reference to the following more detailed description of the preferred embodiments of the invention in conjunction with the accompanying drawings.